ZenithOptimedia lowered its global ad spending forecast for 2015 and 2016, citing a deepening recession in parts of Eastern Europe and slowing growth in China.

ZenithOptimedia lowered its projections for ad spending growth this year, primarily due to economic challenges in Eastern Europe and a slowdown in China’s growth.

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The agency, owned by Publicis Groupe, now projects ad spending to increase 4.4% to $544 billion this year, down from its prior forecast of 4.9% growth. Next year, ad spending is expected to jump 5.3%, boosted by the Summer Olympics and the U.S. presidential election. That’s slightly below its prior projection of 5.6% growth.

Even with the reductions, ZenithOptimedia said the forecasts are still well above the average growth rate of 2.8% for the last 10 years.

The health of emerging markets is closely watched by advertisers who have invested heavily in these countries in recent years to offset the slower growth in more mature markets like Western Europe and the U.S. Now, ZenithOptimedia is warning that some of the growth that marketers have been chasing may be moderating faster than expected.

On Monday, ZenithOptimedia said ad spending in Eastern Europe will sharply decline this year amid ongoing conflict in Ukraine and the impact of economic sanctions and a withdrawal of international investment in Russia. Ad spending has been further hurt by the sharp decline in the price of oil– Russia’s main export– and the devaluation of Ukrainian and Russian currencies. The problems have since spread to Belarus, which primarily trades with Russia, ZenithOptimedia said.

The agency now projects ad spending in Ukraine to topple 62% this year, while Russia is expected to shrink by 16.5%. Belarus’ ad spending is expected to fall 33.5%. However, the steep decline in these markets account for just 2.1% of the world’s ad spending and won’t derail global growth, the agency said.

Meanwhile, China’s economic growth is slowing as the technology gap with mature markets narrows. ZenithOptimedia projects Chinese ad spending will increase 9.1% this year, below the 10.5% annual growth it averaged over the past five years. ZenithOptimedia expects the average growth in China’s ad market of 8.5% a year between 2014 and 2017.

A bright spot for marketers continues to be online video, with ZenithOptimedia estimating the fastest-growing ad category will expand 29 percent annually to reach $23.3 billion in 2017.